Daily was in custody Saturday, charged with aggravated assault, Cpl. Illana Spellman of the Gwinnett County police said.

"It's been confirmed that the Duluth police officer was the aggressor in this case," Spellman said.

Phillips, 37, required surgery at Gwinnett Medical Center. There was no immediate response to a call seeking comment from the hospital Saturday morning.

"It's been baffling to us why this situation even occurred," said Duluth Police Chief Randy Belcher. "It's an embarrassment to this agency."

Phillips, who was wearing his uniform and in a marked police car, was driving to his home in Gwinnett County, police said. He was flagged down by someone who had seen Daily involved in a physical altercation with a woman in a sport-utility vehicle.

Daily, who lives in the area, was off duty and in civilian clothing but was wearing a bulletproof vest, police said.

Police did not know what relationship Daily had with the woman or what started the confrontation. The woman, who was not identified, later was hospitalized for minor injuries she suffered before the shooting started, police said.

Belcher described Daily as "an outstanding officer" and said he was suspended while the investigation is under way.